DBS Group Holdings, Singapore's biggest lender, posted a 6 percent drop in second-quarter profit, hit by a sharp jump in provisions for bad loans as firms in the oil and gas services sector struggle to service debt.

DBS's net profit came in at S$1.05 billion ($780 million) in the three months ended June, versus a S$1.12 billion profit a year earlier.

This is line with an average forecast of S$1.051 billion from six analysts polled by Reuters. The poll was taken before DBS disclosed its S$700 million exposure to troubled oilfield services firm Swiber Holdings.

DBS said bad debt charges more than doubled to S$366 million as a result of the net charges of S$150 million for Swiber.